Prenatal exposure to traffic-related air pollution and risk of early childhood cancers

Geographic Variation in Mortality Among Children and Adolescents Diagnosed With Cancer in Tennessee. Does Race Matter?

Cancer is one of the leading causes of death among children in the United States. Previous research has examined geographic variation in cancer incidence and survival, but the geographic variation in mortality among children and adolescents is not as well understood. The purpose of this study was to investigate geographic variation by race in mortality among children and adolescents diagnosed with cancer in Tennessee. Using an innovative combination of spatial and nonspatial analysis techniques with data from the 2004-2011 Tennessee Cancer Registry, pediatric deaths were mapped and the effect of race on the proximity to rural areas and clusters of mortality were explored with multivariate regressions. The findings revealed that African American children and adolescents in Tennessee were more likely than their counterparts of other races to reside in rural areas with close proximity to mortality clusters of children and adolescents with a cancer. Findings have clinical implications for pediatric oncology nurses regarding the delivery of supportive care at end of life for rural African American children and adolescents.

Traffic-related air pollution and the incidence of childhood central nervous system tumors: Texas, 2001-2009

BACKGROUND

Due to increasing concerns regarding air pollution and childhood cancer, we conducted a population-based study evaluating the association between traffic-related hazardous air pollutants (1,3-butadiene, benzene, diesel particulate matter [DPM]) and the incidence of childhood central nervous system (CNS) tumors.

PROCEDURE

Information on children diagnosed with a CNS tumor at <15 years of age, in Texas, for the period of 2001-2009 (n = 1,949) was obtained from the Texas Cancer Registry. Information on the corresponding at-risk population was obtained from the United States (U.S.) Census. Annual census tract-level pollutant concentrations, estimated by the U.S. Environmental Protection Agency, were categorized based on quartiles (low, medium, medium-high, and high) of the statewide distribution. Multivariable Poisson regression was used to calculate adjusted incidence rate ratios (aIRR). Juvenile pilocytic astrocytomas (JPAs) (n = 384), other astrocytomas (n = 372), ependymomas (n = 142), medulloblastomas (n = 235), and primitive neuroectodermal tumors (PNET) (n = 47) were evaluated.

RESULTS

Census tracts with medium and medium-high 1,3-butadiene concentrations had higher astrocytoma incidence rates (aIRR [95% confidence interval (CI)]: 1.46 [1.05-2.01] and 1.69 [1.22-2.33], respectively) compared with low concentrations. Census tracts with medium DPM concentrations had higher astrocytoma (aIRR [95%CI]: 1.42 [1.05-1.94]) and medulloblastoma (aIRR [95%CI]: 1.46 [1.01-2.12]) incidence rates compared with low concentrations. Increased concentrations of 1,3-butadiene and benzene were strongly associated with increased PNET incidence rates, but were not statistically significant. No associations were detected with JPA or ependymoma incidence.

CONCLUSIONS

In one of the largest studies of its kind, our results suggest positive associations between hazardous air pollutants and incidence of astrocytoma (1,3-butadiene and DPM) and medulloblastoma (DPM).

Exposure to ambient air pollution in Canada and the risk of adult leukemia

There is a paucity of studies investigating adult leukemia and air pollution. To address this gap, we analyzed data from a Canadian population-based case-control study conducted in 1994-1997. Cases were 1064 adults with incident leukemia and controls were 5039 healthy adults. We used data from satellites and fixed-site monitoring stations to estimate residential concentrations of NO2 and fine particulate matter (PM2.5) for the period prior to diagnosis, starting in 1975 and ending in 1994. We modeled the average annual exposure of each subject. Odds ratios (OR) and their 95% confidence intervals (CI) were estimated using logistic regression, adjusted for age, gender, province, smoking, education, body mass index, income, and self-reported exposures to ionizing radiation and benzene. We found an 'n-shaped' response function between exposure to NO2 and all forms of leukemia: from the tenth percentile to the median (4.51 to 14.66 ppb), the OR was 1.20; 95% CI: 0.97-1.48 and from the 75th percentile to the 90th (22.75 to 29.7 ppb), the OR was 0.79; 95% CI 0.68-0.93. For PM2.5 we found a response function consistent with a linear model, with an OR per 10 μg/m(3) of 0.97 (95% CI 0.75-1.26). For chronic lymphocytic leukemia we found response functions that were consistent with a simple linear model, with an OR per 5 ppb of NO2 of 0.93 (95% CI 0.86-1.00) and an OR per 10 μg/m(3) of PM2.5 of 0.62 (95% CI 0.42-0.93). In summary, for chronic lymphocytic leukemia we found no evidence of an association with air pollution and with all forms of leukemia we found weak evidence of an association only at low concentrations of NO2. It is possible that these inconsistent results may have arisen because of unaccounted urban/rural differences or possibly from a selection effect, especially among controls.

Retinoblastoma and ambient exposure to air toxics in the perinatal period

We examined ambient exposure to specific air toxics in the perinatal period in relation to retinoblastoma development. Cases were ascertained from California Cancer Registry records of children diagnosed between 1990 and 2007 and matched to California birth certificates. Controls were randomly selected from state birth records for the same time period. We chose 27 air toxics for the present study that had been listed as possible, probable, or established human carcinogens by the International Agency for Research on Cancer. Children (103 cases and 30,601 controls) included in the study lived within 5 miles of an air pollution monitor. Using logistic regression analyses, we modeled the risk of retinoblastoma due to air toxic exposure, separately for exposures in pregnancy and the first year of life. With a per interquartile range increase in air toxic exposure, retinoblastoma risk was found to be increased with pregnancy exposure to benzene (OR=1.67, 95% CI: 1.06, 2.64) and other toxics which primarily arise from gasoline and diesel combustion: toluene, 1,3-butadiene, ethyl benzene, ortho-xylene, and meta/para-xylene; these six toxics were highly correlated. Retinoblastoma risk was also increased with pregnancy exposure to chloroform (OR=1.35, 95% CI: 1.07, 1.70), chromium (OR=1.29, 95% CI: 1.04, 1.60), para-dichlorobenzene (OR=1.24, 95% CI: 1.04, 1.49), nickel (OR=1.48, 95% CI: 1.08, 2.01), and in the first year of life, acetaldehyde (OR=1.62, 95% CI: 1.06, 2.48). Sources of these agents are discussed.

Heck J, Malagoli C, Del Giovane C, Vinceti M. A review and meta-analysis of outdoor air pollution and risk of childhood leukemia

Leukemia is the most frequent malignant disease affecting children. To date, the etiology of childhood leukemia remains largely unknown. Few risk factors (genetic susceptibility, infections, ionizing radiation, etc.) have been clearly identified, but they appear to explain only a small proportion of cases. Considerably more uncertain is the role of other environmental risk factors, such as indoor and outdoor air pollution. We sought to summarize and quantify the association between traffic-related air pollution and risk of childhood leukemia, and further examined results according to method of exposure assessment, study quality, leukemia subtype, time period, and continent where studies took place. After a literature search yielded 6 ecologic and 20 case-control studies, we scored the studies based on the Newcastle-Ottawa Scale. The studies assessed residential exposure to pollutants from motorized traffic by computing traffic density in the neighboring roads or vicinity to petrol stations, or by using measured or modeled nitrogen dioxide and benzene outdoor air levels. Because heterogeneity across studies was observed, random-effects summary odds ratios (OR) and 95% confidence intervals (CI) were reported. Whenever possible we additionally conducted stratified analyses comparing acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). Limiting the analysis to high-quality studies (Newcastle-Ottawa Scale ≥ 7), those using traffic density as the exposure assessment metric showed an increase in childhood leukemia risk in the highest exposure category (OR = 1.07, 95% CI 0.93-1.24). However, we observed evidence of publication bias. Results for NO2 exposure and benzene showed an OR of 1.21 (95% CI 0.97-1.52) and 1.64 (95% CI 0.91-2.95) respectively. When stratifying by leukemia type, the results based upon NO2 were 1.21 (95% CI 1.04-1.41) for ALL and 1.06 (95% CI 0.51-2.21) for AML; based upon benzene were 1.09 (95% CI 0.67-1.77) for ALL and 2.28 (95% CI 1.09-4.75) for AML. Estimates were generally higher for exposures in the postnatal period compared to the prenatal period, and for European studies compared to North American studies. Overall, our results support a link between ambient exposure to traffic pollution and childhood leukemia risk, particularly due to benzene.

Maternal diet during pregnancy and unilateral retinoblastoma

PURPOSE

Previous studies have suggested a role for parental diet in childhood cancer prevention, but there are few studies of retinoblastoma. The aim of this study was to examine the relation between maternal diet and unilateral retinoblastoma.

METHODS

A case-control study of 163 unilateral RB cases and 136 controls ascertained information on maternal diet during pregnancy using a standardized food frequency questionnaire. Logistic regression was used to assess the relation between retinoblastoma and food groups and dietary patterns.

RESULTS

We observed a negative association between retinoblastoma and intake of fruit [odds ratio (OR) 0.38, 95 % confidence interval (CI) 0.14-1.02]. Positive associations were seen with intake of cured meats (OR 5.07, 95 % CI 1.63-15.70) and fried foods (OR 4.89, 95 % CI 1.72-13.89). A food pattern of high fruits and vegetables and low fried food and sweets was negatively associated with disease (OR 0.75, 95 % CI 0.61-0.92).

CONCLUSION

Our study provides preliminary evidence that mothers who consume diets higher in fruit and lower in fried foods and cured meats during pregnancy may reduce the risk of unilateral retinoblastoma in their offspring.

Impact of fine particles in ambient air on lung cancer

Recently, the International Agency for Research on Cancer (IARC) has classified outdoor air pollution and the particulate matter component of outdoor air pollution as class I carcinogen. Air pollution is consistently associated with lung cancer in epidemiologic and experimental studies. The IARC assessment is specifically designed as hazard identification, and it does not quantify the magnitude of the cancer risk. This article addresses the magnitude of the lung cancer risk in the population due to ambient air pollution exposure.

Risk of leukemia in relation to exposure to ambient air toxics in pregnancy and early childhood

There are few established causes of leukemia, the most common type of cancer in children. Studies in adults suggest a role for specific environmental agents, but little is known about any effect from exposures in pregnancy to toxics in ambient air. In our case-control study, we ascertained 69 cases of acute lymphoblastic leukemia (ALL) and 46 cases of acute myeloid leukemia (AML) from California Cancer Registry records of children <age 6, and 19,209 controls from California birth records within 2 km (1.3 miles) (ALL) and 6 km (3.8 miles) (AML) of an air toxics monitoring station between 1990 and 2007. Information on air toxics exposures was taken from community air monitors. We used logistic regression to estimate the risk of leukemia associated with one interquartile range increase in air toxic exposure. Risk of ALL was elevated with 3(rd) trimester exposure to polycyclic aromatic hydrocarbons (OR=1.16, 95% CI 1.04, 1.29), arsenic (OR=1.33, 95% CI 1.02, 1.73), benzene (OR=1.50, 95% CI 1.08, 2.09), and three other toxics related to fuel combustion. Risk of AML was increased with 3rd trimester exposure to chloroform (OR=1.30, 95% CI 1.00, 1.69), benzene (1.75, 95% CI 1.04, 2.93), and two other traffic-related toxics. During the child's first year, exposure to butadiene, ortho-xylene, and toluene increased risk for AML and exposure to selenium increased risk for ALL. Benzene is an established cause of leukemia in adults; this study supports that ambient exposures to this and other chemicals in pregnancy and early life may also increase leukemia risk in children.

An exploratory study of ambient air toxics exposure in pregnancy and the risk of neuroblastoma in offspring

Little is known about the etiology of neuroblastoma, the most common cancer in infancy. In this study, we examined maternal exposure to ambient air toxics in pregnancy in relation to neuroblastoma in the child. We ascertained all cases of neuroblastoma listed in the California Cancer Registry 1990-2007 that could be linked to a California birth certificate, and controls were selected at random from California birth records. Average air toxics exposures during pregnancy were determined based upon measures from community-based air pollution monitors. The study included 75 cases and 14,602 controls who lived with 5 km of an air pollution monitor, and we additionally examined results for those living within a smaller radius around the monitor (2.5 km). Logistic regression was used to determine the risk of neuroblastoma with one interquartile range increase in air toxic exposure. Neuroblastoma risk was increased with higher maternal exposure to carbon tetrachloride (OR=2.65, 95%CI 1.07, 6.53) and polycyclic aromatic hydrocarbons (OR=1.39, 95%CI 1.05, 1.84), particularly indeno(1,2,3-cd)pyrene and dibenz(a,h)anthracene. Hexavalent chromium was associated with neuroblastoma at the 5 km distance (OR=1.32, 95%CI 1.00, 1.74) but not at the 2.5 km distance. This is one of the first studies to report associations between neuroblastoma and these air toxics.

Childhood cancer and traffic-related air pollution exposure in pregnancy and early life

BACKGROUND

The literature on traffic-related air pollution and childhood cancers is inconclusive, and little is known on rarer cancer types.

OBJECTIVES

We sought to examine associations between childhood cancers and traffic-related pollution exposure.

METHODS

The present study included children < 6 years of age identified in the California Cancer Registry (born 1998-2007) who could be linked to a California birth certificate (n = 3,590). Controls were selected at random from California birthrolls (n = 80,224). CAlifornia LINE Source Dispersion Modeling, version 4 (CALINE4) was used to generate estimates of local traffic exposures for each trimester of pregnancy and in the first year of life at the address indicated on the birth certificate. We checked our findings by additionally examining associations with particulate matter (≤ 2.5 μm in aerodynamic diameter; PM2.5) pollution measured by community-based air pollution monitors, and with a simple measure of traffic density.

RESULTS

With unconditional logistic regression, a per interquartile range increase in exposure to traffic-related pollution during the first trimester (0.0538 ppm carbon monoxide, estimated using CALINE4) was associated with acute lymphoblastic leukemia [ALL; first trimester odds ratio (OR) = 1.05; 95% CI: 1.01, 1.10]; germ cell tumors (OR = 1.16; 95% CI: 1.04, 1.29), particularly teratomas (OR = 1.26; 95% CI: 1.12, 1.41); and retinoblastoma (OR = 1.11; 95% CI: 1.01, 1.21), particularly bilateral retinoblastoma (OR = 1.16; 95% CI: 1.02, 1.33). Retinoblastoma was also associated with average PM2.5 concentrations during pregnancy, and ALL and teratomas were associated with traffic density near the child's residence at birth.

CONCLUSIONS

We estimated weak associations between early exposure to traffic pollution and several childhood cancers. Because this is the first study to report on traffic pollution in relation to retinoblastoma or germ cell tumors, and both cancers are rare, these findings require replication in other studies.